json与java对象的转换,以及struts2对json的支持,实现ajax技术

public static void javabean2Json()
    {
        City city = new City(1,"广州");
        JSONArray jsonArray = JSONArray.fromObject(city);
        String jsonJAVA = jsonArray.toString();
        System.out.println(jsonJAVA);
        //[{"id":1,"name":"广州"}]
    }
    
    public static void list2json()
    {
        List<City> cityList = new ArrayList<City>();
        cityList.add(new City(1,"广州"));
        cityList.add(new City(2,"深圳"));
        
        Province province = new Province(1,"广东",cityList);
        
        //[{"id":1,"cityList":[{"id":1,"name":"广州"},{"id":2,"name":"深圳"}],"name":"广东"}]
        JSONArray jsonArray = JSONArray.fromObject(province);
        String jsonJAVA = jsonArray.toString();
        System.out.println(jsonJAVA);
        //List集合[{"id":1,"name":"广州"},{"id":2,"name":"深圳"}]
    }
    
    public static void set2json()
    {
        Set<City> citySet= new HashSet<City>();
        citySet.add(new City(1,"广州"));
        citySet.add(new City(2,"深圳"));
        JSONArray jsonArray = JSONArray.fromObject(citySet);
        String jsonJAVA = jsonArray.toString();
        System.out.println(jsonJAVA);
        //[{"id":1,"name":"广州"},{"id":2,"name":"深圳"}]
    }
    public static void map2json()
    {
        List<City> cityList = new ArrayList<City>();
        cityList.add(new City(1,"广州"));
        cityList.add(new City(2,"深圳"));
        
        Map<String,Object> map = new HashMap<String,Object>();
        map.put("total", cityList.size());//表示集合的长度
        map.put("rows", cityList);//表示集合
        /**
         * [{"total":2,"rows":[{"id":1,"name":"广州"},{"id":2,"name":"深圳"}]}]
         */
        
        JSONArray jsonArray = JSONArray.fromObject(map);
        String jsonJAVA = jsonArray.toString();
        jsonJAVA = jsonJAVA.substring(1,jsonJAVA.length()-1);
        System.out.println(jsonJAVA);
        //[{"id":1,"name":"广州"},{"id":2,"name":"深圳"}]
    }
    
    public static void main(String[] args) {
        // TODO Auto-generated method stub
//        javabean2Json();
//        list2json();
//        set2json();
        map2json();
    }

 <!-- 配置拦截器 -->
  <filter>
      <filter-name>struts2</filter-name>
      <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
  </filter>
  
  <filter-mapping>
      <filter-name>struts2</filter-name>
      <url-pattern>/*</url-pattern>
  </filter-mapping> 

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>

    <!-- 配置struts2 -->
    <!--<package name="checknode" extends="struts-default" namespace="/user">
        <action name="check" class="cn.itcast.js_02.checkcode.CheckcodeAction" method="check">
        </action>
    </package>-->
    
    <package 
    name="province" 
    extends="json-default" 
    namespace="/">
    
    <!-- 配置全局结果 -->
    <global-results>
        <result  name="success" type="json"></result>
    </global-results>
        <action 
        name="findCityByProvince" 
        class="cn.itcast.js_02.provincecityarea.ProvinceCityArea"
         method="findCityByProvince">
        </action>
        
        <action 
        name="findAreaByCity" 
        class="cn.itcast.js_02.provincecityarea.ProvinceCityArea"
         method="findAreaByCity">
        </action>
    </package>
    
    
</struts>

package cn.itcast.js_02.provincecityarea;

public class Bean {
    
    private String province;
    private String city;
    
    public Bean() {
        // TODO Auto-generated constructor stub
    }

    public String getProvince() {
        return province;
    }

    public void setProvince(String province) {
        this.province = province;
    }

    public String getCity() {
        return city;
    }

    public void setCity(String city) {
        this.city = city;
    }
}

package cn.itcast.js_02.provincecityarea;

import java.util.ArrayList;
import java.util.List;

import com.opensymphony.xwork2.ActionSupport;

public class ProvinceCityArea extends ActionSupport {
    
    private Bean bean;
    public void setBean(Bean bean) {
        this.bean = bean;
    }
    public Bean getBean() {
        return bean;
    }

    public String findCityByProvince() throws Exception {
        // TODO Auto-generated method stub
        cityList = new ArrayList<String>();
        if("湖北".equals(bean.getProvince()))
        {
            cityList.add("武汉");
            cityList.add("孝感");
            cityList.add("黄冈");
        }else if("湖南".equals(bean.getProvince()))
        {
            cityList.add("长沙");
            cityList.add("株洲");
            cityList.add("岳阳");
            cityList.add("湖南");
        }else if("江西".equals(bean.getProvince()))
        {
            cityList.add("南昌");
            cityList.add("南昌");
            cityList.add("南昌");
            cityList.add("南昌");
        }
        
        //配置让struts2自动将List/Set/Map<String>转换为JSON文本
        return this.SUCCESS;
    }
    
    /**
     * 通过城市查找区域
     * @return
     * @throws Exception
     */
    
    public String findAreaByCity() throws Exception {
        // TODO Auto-generated method stub
        areaList = new ArrayList<String>();
        if("武汉".equals(bean.getCity()))
        {
            areaList.add("AA");
            areaList.add("BB");
            areaList.add("CC");
        }else if("南昌".equals(bean.getCity()))
        {
            areaList.add("DD");
            areaList.add("EE");
            areaList.add("FF");
        }else if("长沙".equals(bean.getCity()))
        {
            areaList.add("GG");
            areaList.add("HH");
            areaList.add("II");
        }
        
        //配置让struts2自动将List/Set/Map<String>转换为JSON文本
        return this.SUCCESS;
    }
    
    private List<String> cityList;
    private List<String> areaList;
    public List<String> getAreaList() {
        return areaList;
    }
    public List<String> getCityList()
    {
        return this.cityList;
    }
}

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";
%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <base href="<%=basePath%>">
    
    <title>struts2实现三级联查询</title>
    
    <meta http-equiv="pragma" content="no-cache">
    <meta http-equiv="cache-control" content="no-cache">
    <meta http-equiv="expires" content="0">    
    <meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
    <meta http-equiv="description" content="This is my page">
    <!--
    <link rel="stylesheet" type="text/css" href="styles.css">
    -->
  </head>
  <body>
  <select id="provinceID" style="width:111px">
      <option>请选择省份</option>
      <option>湖北</option>
      <option>湖南</option>
      <option>江西</option>
  </select>
  
  <select id="cityID" style="width:111px">
      <option>请选择城市</option>
  </select>
  
   <select id="areaID" style="width:111px">
      <option>请选择区域</option>
  </select>
   <script type="text/javascript" src="js/ajax.js"></script>
   <script type="text/javascript">
   document.getElementById("provinceID").onchange = function()
   {
       var province = this[this.selectedIndex].innerHTML;
       //清除之前的样式
       var cityElement = document.getElementById("cityID");
       cityElement.options.length = 1;
       //当省份发生变化时,区域也会发生变化
       var areaElement = document.getElementById("areaID");
       areaElement.options.length = 1;
       if("选择省份"!=province)
       {
           //NO1)
           var ajax = createAjax();
           //NO2)
           var method = "POST";
           var url = "${pageContext.request.contextPath}/findCityByProvince?time="+new Date().getTime();
           ajax.open(method, url);
           //NO3)
           ajax.setRequestHeader("content-type", "application/x-www-form-urlencoded");
           //NO4)
           var content = "bean.province="+province;
           ajax.send(content);
           //------------------------->等待
           //NO5)
           ajax.onreadystatechange = function()
           {
               if(ajax.readyState == 4)
               {
                   if(ajax.status == 200)
                   {
                       //NO6)返回JAVA
                       var jsonJAVA = ajax.responseText;
                       var p = eval("("+jsonJAVA+")");
                       var array = p.cityList;
                       var size = array.length;
                       for(var i=0;i<size;i++)
                       {
                           var city=array[i];
                           var option = document.createElement("option");
                           option.innerHTML = city;
                           cityElement.appendChild(option);
                       }
                   }
               }
           }
       }
   }
   
   
   document.getElementById("cityID").onchange = function()
   {
       var city = this[this.selectedIndex].innerHTML;
       //清除之前的数据
       var areaElement = document.getElementById("areaID");
       areaElement.options.length = 1;
       if("请选择城市"!=city)
       {
           //NO1)
           var ajax = createAjax();
           //MO2)    
           var method = "POST";
           var url = "${pageContext.request.contextPath}/findAreaByCity?time="+new Date().getTime();
           ajax.open(method,url);
           //NO3)
           ajax.setRequestHeader("content-type", "application/x-www-form-urlencoded");
           //NO4)
           var content = "bean.city="+city;
           ajax.send(content);
           
           //----------------------等待
           ajax.onreadystatechange = function()
           {
               //NO5)
               if(ajax.readyState == 4)
               {
                   if(ajax.status == 200)
                   {    
                       //NO6)
                       var jsonJAVA = ajax.responseText;
                       var jsonJS = eval("("+jsonJAVA+")");
                       var array = jsonJS.areaList;
                       var size = array.length;
                       for(var i=0;i<size;i++)
                       {
                           var area = array[i];
                           var option = document.createElement("option");
                           option.innerHTML = area;
                           areaElement.appendChild(option);
                       }
                   }
               }
           }
       }
       
   }
   </script>
  </body>
  <form action="" enctype="application/x-www-form-urlencoded"></form>
</html>
在这中间出了一些问题,大部分是因为写错了方法名称或属性名例如:ajax.onreadystatechange
最后再附上源码地址:https://github.com/blench/js_day02.git